Magnetic trip device



Jan. 5, 1960 E. P. DESSERT EI'AL 2,920,161

MAGNETIC TRIP DEVICE Filed Jan. 16, 1959 2 Sheets-Sheet 1 INVENTOR Q 59zywdfzpjdfls'eif erner )1 Kass 35 74 821:: fig:

Jan. 5, 1960 E. P. DESSERT ET AL 2,920,161

MAGNETIC TRIP DEVICE Filed Jan. 16, 1959 2 Sheets-Sheet 2 70 a; if 5 50MAGNETIC TRIP DEVICE Edward P. Dessert, Detroit, Werner F. Kussy,Birmingham, and Tadeusz J. Rys, Detroit, Mich., assiguors to Square DCompany, Detroit, Mich., a corporation of Michigan Application January16, 1959, Serial No. 787,229

Claims. (Cl. 20095) This invention relates generally to electric circuitbreakers and more particularly to an improved adjustablemagnetically-responsive trip device for controlling the automaticopening of an electric circuit breaker.

Automatic electric circuit breakers having magnetically-responsive tripdevices are often used to protect branch circuits supplying electricmotors or other electric translating devices requiring high initial orinrush currents. The magnetically-responsive trip device of such circuitbreakers should be adjustable so that tripping of the circuit breakercan be caused to occur at different predetermined current values. Topermit use of the same circuit breaker in circuits of widely differentloading, selectively, the trip device must be adjustable throughout awide range of current values.

Accordingly, an object of the present invention is to provide animproved magnetic trip device for a circuit breaker that can be adjustedto respond throughout a relatively Wide range of current values.

Since it is desirable that a magnetic trip device he adjustable so as tonot respond to normal inrush current yet be operative to providepositive protection upon the occurrence of currents only slightlygreater than the normal inrush current, a trip device should beadjustable in relatively small increments of current value throughoutits range of adjustment.

Therefore, another object is to provide an improved magnetic trip devicethat can be adjusted in relatively small increments of current valuethroughout its full range of adjustment.

To be acceptable for industrial applications, a trip device shouldaccurately maintain its initial calibration as well as its currentresponse setting even though the circuit breaker is subjected to adverseoperating conditions including severe vibration.

Another object is to provide an improved trip device for a circuitbreaker which maintains its initial calibration as well as its currentresponse setting for long periods of time and without material deviationdue to adverse operating conditions.

A further object is to provide a magnetic trip device including anadjustment means operable to vary simultaneously two factors affectingthe amount of magnetic flux required to operate the trip device.

A more detailed object is to provide a magnetic trip device comprising amagnetic core, a winding around said core, a pivoted magnetic armatureoperatively related with said core, an armature spring biasing saidarmature to its open position, and an adjustment means operable toincrease concurrently the biasing force of the armature spring and theair gap between the core and armature.

Other objects and advantages of the present invention will becomeapparent from the following description, wherein reference is made tothe drawings, in which:

Fig. 1 is a side elevation of a trip device in accordance a UnitedStatesPatent O "ice with the present invention, partially in section,and shown in cooperative relation with a circuit breaker,

Fig. 2 is an enlarged side elevation of the trip device as shown in Fig.1,

Fig. 3 is a fragmentary top view of the circuit breaker taken asindicated at IIIIII of Fig. 2 and showing the index positions of severalof the trip devices in a multipole circuit breaker,

Fig. 4 is a side elevation of the trip device, similar to Fig. 2, butshowing the device in the adjusted position requiring maximum current totrip the device,

Fig. 5 is a side elevation of the trip device, similar to Fig. 2 butshowing the armature attracted to the core,

Fig. 6 is a view of the trip device taken as indicated at VI-VI of Fig.2,

Fig. 7 is a cross-sectional view taken as indicated at VIIVII of Fig. 6,and

Fig. 8 is a cross-sectional view taken as indicated at VIIIVIII of Fig.2.

Referring to Fig. 1, a trip device 10 in accordance with this inventionis shown in association with a multi-pole circuit breaker 11 of thegeneral type described and claimed in W. T. Allen et al. Patent No.2,814,693, issued November 26, 1957. It will be obvious that the tripdevice can be used as well with other multipole circuit breakers or withsingle pole circuit breakers. The circuit breaker 11 has a housing 12 ofinsulating material that serves to enclose and support the operatingcomponents of the circuit breaker. The trip device for each pole of thecircuit breaker is identical with the others, and therefore only onepole is shown and described. A terminal strip 14 having a fixed contact15 secured thereto, as by welding, is suitably mounted at one endportion of the housing 12 and passes through the housing wall forconnection to an external source of electrical energy (not shown). Amovable contact 16 on a movable contact carrier 18 cooperates with thefixed contact 15 to make and break an electrical circuit through thepole, as will be described. The contact carrier 18 is pivotallysupported on a transverse pin 19 suitably mounted within the housing 12.An operating member 20 is also pivotally supported on the transverse pin19 and receives, in a cutout portion 21, an interiorly projecting endportion 22 of a manual operator 24. The manual operator 24 is supportedfor rotation, with respect to the housing 12, on a pair ofaxially-aligned trunnions 25 supported in suitable bearing recesses (notshown) in the housing 12. A lever 28, rotatably secured at one endportion to the operating member 20, carries, at its other end portion, apin 29 which is slidably received in a slot 30 formed in the contactcarrier 18. A releasable member 31, pivotally mounted on a transversepin 32 which is fixedly supported within the housing 12, is providedwith an upstanding hook-like portion 34 to which one end of an operatingspring 35 is fastened. The other end of the operating spring 35 isfastened to the pin 29. The releasable member 31 is thus biased forclockwise rotation about the pin 32 but is normally restrained from suchrotation by engagement of a latching portion 38 thereof with atransverse trip bar 39 common to the several poles.

As will become apparent, upon automatic operation of the circuitbreaker, the trip bar 39 rotates clockwise, as shown in Fig. 1, abouttrunnions 40 thereon and retracts from its engagement with the latchingportion 38 of the releasable member 31 to allow the releasable member 31to rotate about the base pin 32 under the bias of the operating spring35. This rotation of the releasable member 31 carries the line of actionof the spring 35 upwardly across a line between the pin 29 and pivotalconnection of the lever 28 to the operating member 20 Patented Jan. 5,1960- thereby biasing the contact carrier 18 to turn counterclockwise toseparate the contacts 15 and 16.

Referring principally to Fig. 2, the trip device 11) comprises aU-shaped magnetic core 41 having a bight portion 42 and spaced legportions 44-. The core 41 may be supported within the enclosure 12 as bya pair of shoulders 45 that extend outwardly from opposite sides nearthe bight portion 42 and are received in respective grooves (not shown)formed in the side walls of the enclosure 12. Each of the leg portions44 is provided with a planar pole face 46. An electrical conductor 48 isWound about the bight portion 42 of the magnetic core 41 and isconnected at one end to a terminal member 49 as shown in Fig. l. Theterminal member 49 is secured to an external ledge on the enclosure 12as by a screw 59. A conventional solderless connector 51 is engaged withthe terminal member 4% to facilitate connection of the circuit breaker11 to an external load. The other end of the conductor 48 iselectrically connected through a flexible conductor 52 to the movablecontact carrier 18.

in accordance with this invention, an armature 53 is supported forrotation with respect to the core 41 by a pin 54 that passes throughspaced ears 55' formed on the armature 53 and is received in spacedbearing recesses 56 formed on the upper edges of the leg portions 44 ofthe core 41. The armature 53 is provided with an integral fian e '7formed to provide a spring retainer cup 58 for the acceptance of thelower end of an armature spring 59. The armature 53 has an upperextension 66 that limits rotation of the armature under the bias of thespring 59, as will be described, and a lower extension 61 that isoperatively aligned with the pole faces 46 of the core 43. Preferably,the ears 55, flange 57, retainer cup 58 and upper extension 60 are madeof non-magnetic material and the lower extension 61 is made of magneticmaterial.

The lower extension 61 of the armature 53 is biased to the unattractedposition, with respect to the pole faces 46 of the core 4-1, by thespring 59. The spring 59 is preferably a helical compression spring andextends between the spring retainer cup 58 and the lower end face of aninitial adjustment screw 62 having an externally threaded lower portion64- that engages an internally threaded central bore 65 of a slidablemember 66. The member 66 is mounted in a U-shaped frame 69 having abight portion 76 and horizontally disposed upper and lower leg portions'71 and '72. The frame 69 is supported within the housing 12 by spacedears 74 extending rearwardly from the bight portion '76 and received inrespective recesses in the housing.

The member 66 is non-circular in cross-section and is received forslidable translation with respect to the frame 69 within a complementarynon-circular cutout 75 in the lower leg portion 72 of the trip frame 69.The non-circular configuration of the member 66 and the cutout 75restrains the member 66 from rotation with respect to the frame 69.Turning of the initial adjustment screw 62 moves it axially with respectto the slidable member 66 thereby changing the length of the spring 59to vary its bias on the armature 53.

The slidable member 66 has a planar upper edge face 76 disposed at anangle other than a right angle with respect to the axis of the initialadjustment screw 62. An upper portion '78 of the initial adjustmentscrew 62 extends above the top edge face 76 and is provided with a slot'7) for the acceptance of a screwdriver to faciiitate turning thereof.

A field adjustment cam 86 of circular cross-section is supported forrotation in a circular cutout 81 in the upper leg portion '71 of theframe 69 in axial alignment with the initial adjustment screw 62 and isprovided with a planar lower edge face 32 that is disposed at the sameangle with the rotative axis thereof as that between the upper edge face76 and the axis of the slidable member 66.

The field adjustment cam 36 is provided with a central bore 84 thataccepts the upper extension 78 of the initial adjustment screw 62. Thefield adjustment cam 80 has an intermediate eccentric cam portion ofgenerally circular configuration having a central axis parallel to, butdisplaced from, the rotative axis of the field adjustment cam 86 (Fig.8) in the direction of the lowermost portion of the lower edge face 82thereof. The cam portion 85 of the field adjustment cam 80- engages theupper extension 611) of the armature 53 and upon turning of the cam 89,positions the lower armature extension 61 different distances from thepole faces 46 of the core 41.

An insulating knob 86 extends through the housing 12 and releasablyengages the field adjustment cam 80. Rotation of the insulating knob 86is transmitted to the field adjustment cam Sit by a hexagonal extension87 which is seated in an upwardly directed hexagonal recess 88 (Fig. 7)in the field adjustment cam 86.

The upper leg portion 71 of the frame 69 has an outer edge face 89generally concentric with the circular cutout portion 81 thereof andprovided with a plurality of equally and circumferentially spacedradially outwardly extending ridges 96 (Fig. 7) which cooperate with anindex spring )1 to index rotation of the field adjustment cam 89.Preferably the index spring 91 is secured to the field adjustment cam 86as by staking.

Adjustment of the trip device 10 to an initial setting is accomplishedby first rotating the cam member 80 so that the planar lower edge face82 thereof is parallel to the planular upper edge face 76 of theslidable member 66. In this position, the eccentric portion 85 of thecam member 86 biases the upper extension 66 of the armature 53 clockwiseabout the pivotal support 55 thereof thus rotating the lower extension61 of the armature 53 to the smallest air gap position with respect tothe pole faces 44 on the magnetic core 41. Further, the slidable member66 is permitted to fully retract into the trip frame 70 under the biasof the spring 59 thereby reducing the effective force of the spring 59on the armature 53. The adjustment screw 62 is then advanced until adesired minimum value of current develops a flux in the magnet core 41sufficient to attract the lower extension 61 of the armature to the polefaces 46 thereof against the bias of the trip spring 59. The initialpositioning of the adjustment screw 62 takes care of variances betweentrip units due to manufacturing tolerances.

After rotation of the initial adjustment screw 62 to an initial setting,the insulating knob 86 is placed over the cam member 80 in interlockingrelationship. If it is desired to increase the amount of currentrequired to energize the trip device 10, the insulating cap 86 and cammember 86, which rotates therewith, are turned with respect to thehousing 12. Rotation of the cam member 80 forces the tubular member 66downwardly because the lowermost area of the planular face 82 of the cammember 8t bears upon the upper face 76 of the slidable member 66. Themaximum adjustment of the trip device 10 is achieved when the lowermostarea of the planar lower edge face 82 is turned to the point where itcontacts the uppermost area of the planar upper edge face 76 of thetubular member 66 (Fig. 4). Upon rotation of the cam member 86, and atthe same time that it is moving the tubular member 66 downwardly, theeccentric portion 85 thereof rotates to reduce the radial distancebetween the outer edge face thereof and the rotative axis of the cam 80,thereby permitting the upper extension 60 of the armature 53 to rotatecounter-clockwise about its pivotal support 50 under the bias of thespring 59. Counter-clockwise rotation of the armature 53 increases theair gap between the lower extension 61 of the armature and the polefaces 46 of the magnetic core 41. In this manner a wide range ofadjustment is achieved for the trip device 10 because the armature 54 isbiased more strongly to the unattracted position simultaneously as theair gap between the lower extension 61 of the armature 54 and the polefaces 44 of the magnetic core 41 is increased. The effect of thissimultaneous adjustment of air gap and armature spring bias is to changethe magnetic flux required within the magnetic core to attract thearmature and trip the circuit breaker.

Upon excessive current flow through the coil 48, a magnetic flux isestablished in the core 41 and the lower extension 61 of the armature 53is attracted toward the pole faces 46 thereof (Fig. 5). As the armature53 rotates in the clockwise direction, the upper extension 60 thereofbiases the cross bar 39 in a clockwise direction thereby retracting thecross bar from engagement with the latching portion 38 of the releasablemember 31 and allowing the releasable member 34 to rotate about the pin32 thereby opening the contacts 15 and 16 with a snap action.

Upon rotation of the manual operator 24 to the open and closedpositions, the operating member 20 is biased alternately in oppositedirections about the pin 19. Movement of the operating member carriesthe link 28 across the line of action of the spring 35 to open and closethe contacts 15 and 16 with a snap action, selectively.

What is claimed is:

l. A circuit breaker comprising relatively movable contacts, meansreleasable to eifect opening of said contacts, and a trip deviceoperable to release said releasable means in response to predeterminedelectrical conditions in an electrical circuit containing said circuitbreaker, said trip device comprising a magnetic core, means connected insaid electrical circuit to develop a magnetic flux in said core upon theoccurrence of said condition, a magnetic armature operatively relatedwith said magnetic core so as to be attracted thereto upon theoccurrence of said condition, a first member mounted for movement withrespect to said magnetic core, an initial adjustment screw movable byand with respect to said first member, an armature spring extendingbetween said initial adjustment screw and said armature and biasing saidarmature to an unattracted position with respect to said magnetic core,the bias of said armature spring on said armature being variableuponmovement of said initial adjustment screw with respect to said firstmember and upon movement of said first member with respect to saidmagnetic core, a second member disposed for movement with respect tosaid first member and said magnetic core and engageable with said firstmember, movement of said second member effecting movement of said firstmember with respect to said magnetic core, and an armatu re positioningportion on said second member, engageable with said armature formovement of said armature against the bias of said armature springthereby to determine said unattracted position of said armature withrespect to said magnetic core.

2. A circuit breaker comprising relatively movable contacts, meansreleasable to effect opening of said contacts, and a trip deviceoperable to release said releasable means in response to predeterminedelectrical conditions in an electrical circuit containing said circuitbreaker, said trip device comprising a magnetic core, means connected insaid electrical circuit to develop a magnetic flux in said core upon theoccurrence of said condition, a magnetic armature operatively relatedwith said magnetic core so as to be attracted thereto upon theoccurrence of said condition, a first member mounted for slidabletranslation with respect to said magnetic core, an initial adjustmentscrew threadably engaged with said first member, an armature springextending between said initial adjustment screw and said armature andbiasing said armature to an unattracted position with respect to saidmagnetic core, the bias of said armature spring on said armature beingvariable upon rotation of said initial adjustment screw with respect tosaid first member and upon movement of said first member with respect tosaid magnetic core, and a second member disposed for rotation withrespect to said first member and said magnetic core and engageable withsaid first member, rotation of said second member effecting translationof said first member with respect to said magnetic core, and an armaturepositioning cam on said second member engageable with said armature formovement of said armature against the bias of said armature springthereby to determine said unattracted position of said armature withrespect to said magnetic core.

3. A circuit breaker comprising relatively movable contacts, meansreleasable to efiect opening of said contacts, and a trip deviceoperable to release said releasable means in response to predeterminedelectrical conditions in an electrical circuit containing said circuitbreaker, said trip device comprising a magnetic core, means connected insaid electrical circuit to develop a magnetic flux in said core upon theoccurrence of said condition, a magnetic armature operatively relatedwith said magnetic core so as to be attracted thereto upon theoccurrence of said condition, a first member mounted for slidabletranslation with respect to said magnetic core and having a planar edgeface disposed at an angle other than an angle normal to the direction oftranslation thereof, an armature spring extending between said firstmember and said armature and biasing said armature to an unattractedposition with respect to said magnetic core, the bias of said armaturespring on said armature being variable upon movement of said firstmember with respect to said magnetic core, and a second member disposedfor rotation with respect to said first member, said magnetic corehaving a surface engageable with said edge face of said first member,and rotation of said second member eifecting translation of said firstmember with respect to said magnetic core.

4. A circuit breaker comprising relatively movable contacts, meansreleasable to effect opening of said contacts, and a trip deviceoperable to release said releasable means in response to predeterminedelectrical conditions in an electrical circuit containing said circuitbreaker, said trip device comprising a magnetic core, means connected insaid electrical circuit to develop a magnetic flux in said core upon theoccurrence of said condition, a magnetic armature operatively relatedwith said magetic core so as to be attracted thereto upon the occurrenceof said condition, a first member mounted for translation with respectto said magnetic core having an edge face disposed other than normallyto the direction of translation thereof, an armature spring extendingbetween said first member and said armature and biasing said armature toan unattracted position with respect to said magnetic core, the bias ofsaid armature spring on said armature being variable upon movement ofsaid first member with respect to said magnetic core, a second memberdisposed for movement with respect to said first member and saidmagnetic core and engageable with said edge face of said first member,movement of said second member effecting movement of said first memberwith respect to said magnetic core, and an armature positioning portionon said second member engageable with said armature for movement of saidarmature against the bias of said armature spring thereby to determinesaid unattracted position of said armature with respect to said magneticcore.

5. A circuit breaker in accordance with claim 1 characterized in thatthe magnetic armature of the trip device is mounted on a pivot and turnsabout the pivot upon said attraction to the magnetic core.

No references cited.

